This Section II is concerned with the detailed morphologic study of changes in the musculature, interstitium and intrinsic innervation of the bladder and ureter, and changes in the kidney, of the obstructed feline urinary tract in comparison to sham- operated and normal controls. In regard to the bladder and ureter, the study involves light microscopy, neurohistochemistry and electron microscopy, plus a specially designed program for detailed morphometric analysis of all preparations. The data to be obtained will form the structural basis for interpretation of the various changes in urinary tract function, especially contractility, to be obtained in vivo (Section I) and in vitro (Section III), will correlate directly with in vitro biochemical assays of the bladder and ureter in regard to the smooth muscle and interstitial compartments, and form the morphologic basis for interpretation of observations on the pharmacologic responses and autonomic receptor densities in both organs. In regard to the kidney, light microscopic, electron microscopic, and as needed, immunohistochemical preparations will be studied. The results will be correlated directly in conjunction with renal functional changes, with both the ureteral or vesical dysfunction resulting from different degrees and durations of vesical outlet obstruction.